1. Field of the Invention
The present invention relates generally to field irrigation systems, and more particularly to an improved irrigation system which combines the water efficiency of surface drip irrigation with the flexibility and economic advantages of center pivot or linear move irrigation systems.
2. Description of the Related Art
Conventional mobile irrigation systems may be classified in two general types: center pivot, and linear move. A center pivot irrigation system includes a central pump station which supplies a source of water, and a plurality of towers extending radially from the central pump station and carrying a supply pipe. The supply pipe has a plurality of uniformly spaced sprinkler heads which spray water along the length of the supply pipe. The towers include driven wheels and move in a circular pattern about the central pump station.
A linear move irrigation system includes a plurality of towers with driven wheels, the towers carrying a water supply pipe having sprinkler heads distributed along the pipe. One end of the supply pipe is then connected to a source of water, and the entire pipe is moved in a direction perpendicular to the axis of the pipe, to irrigate a field.
These mobile irrigation systems are popular because of their flexibility and economics. However, the water efficiency of prior art mobile irrigation systems is quite poor. This low water efficiency is mainly due to water evaporation and wind drift, because the sprinkler heads are located high above the ground (typically 15-20 feet) along the supply pipe carried by the mobile towers.
In partial solution to the problems stated above, U.S. Pat. No. 6,343,749, entitled “Mobile Drip Irrigation System” issued to Thom, discloses and claims a mobile drip irrigation system that includes an existing mobile irrigation system with the sprinkler heads removed and drip lines connected to the locations of the removed sprinkler heads. Each drip line includes a drop line extending from the irrigation system supply pipe, generally vertically to a lower end spaced slightly above the ground. A drip hose is connected to the lower end of each drop line and has a plurality of drip irrigation emitters along the length thereof. A weight is attached to the lower end of each drop line to maintain the drop line in a generally vertical orientation as the irrigation system moves through the field. A drip hose is fluidly connected to the lower end of the drop line and extends rearwardly therefrom with substantially its entire length in contact with the ground, including a plurality of drip irrigation emitters uniformly spaced along substantially the entire length thereof. The device is functional when utilized with relatively small fields such as mint fields; however, because it cannot be used effectively in larger fields because it irrigates only at the drop points, i.e. it does not distribute liquid significantly in lateral directions.
U.S. Pat. No. 4,429,831, entitled “Ground Release Irrigation System” issued to G. H. Maddox, discloses an irrigation system is provided wherein a conventional central pivot spray-type system is converted into a ground release system through the use of a plurality of flexible hoses that release the water at ground level. A plurality of perforations at the distal end of the hose provide a spray effect without the water evaporation loss associated with conventional spray systems. Braces also prevent the hoses from swinging sideways and becoming entangled. The '831 system, like the '749 system use drip irrigation; however, release is at the ground level. The hose being located at the ground provides undesired movement which is partially compensated by restraining devices.